Not running on all cylinders

[deduce25]

Here we go,
I recently bought this bike as a non-runner. Cleaned the carbs, tank, filter a million times. Put in fresh plugs and she started but idled rough. The emlusion tubes were oval so I bought new ones. Put them in and now I'm only running on 3 cylinders although it's possible I always have but it was just running so rough I didn't know. Number 1 is only going to 200 degrees and I believe that to be radiant heat. It's getting fuel, compression and spark but I believe it is a weak one. Anyone have any suggestions? What's my first step to diagnose? First time the bike has stumped me so far so it's time to call on the experts.

Thanks
Shane

[JasonRDfan]

Did you check the pilot screws yet? I like to start the bike rev it a little and see if it runs on all 4, so then you'll know if it's just missing at idle. Then will work on the next steps.

[JasonRDfan]

Also get a spark plug, pull the plug wire on the cylinder that's missing and check the spark. If its a good spark I would pull the plug and check color and the gap. Spark, air, fuel, right? Your air is probably good so if you have a good spark it's probably fuel right? So that's why you need to see at what rpm range so you can get some ideas.

[deduce25]

Pilot screws all 3 turns out. Pulled the #1 plug and it was wet. I also pulled the plug, cleaned it and put it against the engine and got spark. Gap is see at .65 and I believe I got a yellowish spark. The sun was out and I had a hard time seeing it. It does sound like it's running on all 4 when I rev it though. Thanks for the quick reply too.

Shane

[JasonRDfan]

If it runs on 4 when you rev it I would look into the pilot jet on the matching carb, see if you can get a good spray of carb cleaner through it. Don't get it on any rubber, pull the diaphragm first carefully sit aside. I would close the gap on the plugs.

[deduce25]

Okay, I attempted to check the resistance of the coils earlier too. at 200ohms on the meter I came out with 4-4.1 and I believe it's outside of the specs. Problem is I'm not exactly sure I did that right. I'm more of a test light type of guy. Pilot jet is the one inside the throat of the carb right? I have a hard time remember the names of all of them. I believe I get fuel in the cylinder but I can't quite remember. My frustration was getting the best of me so I had to button it up and walk away for a while.

[JasonRDfan]

So if it has a weak spark sometimes by closing the gap a little it will run fine, then you may have an idea what's going on at least. Pilot jet sits inside the little tube, make sure the spray goes through the jet real good. Might as well do all the jets again. Don't poke any metal through the jet holes. I heard fishing line works. I've done alot of old bikes and a very good trick is to take the carbs apart, no rubbers, and take an old crock pot, or get one at a thrift store and using antifreeze cook them overnight. Spray them out with carb cleaner, compressed air. Works great. Whats the miles?

[Burtonrider10022]

Have you done a compression test?

[JasonRDfan]

Have you done a compression test?

Lol, that's what I was going to ask him next.
A compression test can give you a heads up with valves too, that's why I was asking the mileage. To get an idea if a possible valve issue.

[deduce25]

23k on the odo. I've sprayed all the jets and ran fishing line. I actual have a gallon of chemical dip but I'm scared losing some unseen rubber bits if I do it. How far do I have to break down the carbs to cook them? Seperate them too?

Compression felt really strong but I don't have actual numbers. Rented a gauge at autozone but it didn't fit. Guess I'll be buying on today

[deduce25]

What should I close the gap too? Also, can I do a compression test without the carbs on? And did I test the coils right? Could it be that easy? Really don't want to just throw parts at it

[fzrbrandon]

I think you said you were getting some spark on the problem cylinder. However, I would check to make sure the plug boot is securely screwed into (and making good contact with) the plug wire. Unscrew the boot and trim the wire back about 1/4” and see if that helps.

[deduce25]

I'll try that when I get home. Thanks

[Sooty]

Had a similar problem on mine, turned out to be the valve stem oil seals. Ran rough when first started as oil was dripping ever so slowly when stood down the inlets of cylinders 2 & 3. Riding about a mile or so the plugs would clean themselves and it would run fine. As the cams & stems are in an oil bath and it is not pressurised it would only drip so no clouds of blue smoke although it would smell a little rich when first started. Went down the usual route of ignition and carbs to no avail until it would not run one day on the middle cylinders at all. Took the plugs out and fired it up running on cylinders 1 & 4 to find oil was coming out of the plug on number 2 cylinder. Fearing the worst of a knackered piston or rings I stripped the motor down and noticed there was oily deposits in the inlet tract of cylinders 2 & 3 (clean on cylinders 1 & 4). Have replaced the valve stem oil seals and the problem has now disappeared, apparently they harden over time and crack. Shine a torch down the inlet tract when you have the carbs off and see if if its bright aluminium, if there are any dark deposits there then chances are its your valve stem oil seals.

[JasonRDfan]

I'll try that when I get home. Thanks

Any updates yet? Did you get her figured out?